Fibronectin has recently been shown to be a major nonspecific opsonin of plasma and to be depleted in severely ill patients. In a small uncontrolled study, restoration of fibronectin by giving cryoprecipitate had a favorable effect on surgical patients with sepsis. If similar favorable effects can be shown in larger, controlled studies, there is likely to be a great demand for fibronectin preparations. Our research has three goals: (1) to devise a safe, efficient, and economical method for isolating fibronectin from Cohn fraction I or plasm; (2) to devise and evaluate methods for assaying the biological effectiveness of fibronectin preparations; and (3) to devise a simple, rapid method for quantitating fibronectin concentration in blood. The isolation from Cohn fraction I will employ the following steps: (1) heat precipitation to remove fibrinogen, (2) adsorption of fibronectin to insolubilized gelatin, collagen fragments, or synthetic ligands followed by desorption with chaotic salts or small collagen-like peptides, and (3) concentration of fibronectin by precipitation with ethanol or glycine. Fibronectin from plasma will be absorbed directly to the insolubulized ligands. Fibronectin preparations will be stored as frozen solutions, as pastes, or after lyophilization, and will be assayed at intervals for proteolytic degradation, ability to bind to collagen and fibrin, ability to mediate uptake of gelatin-coated colloids by reticuloendothelial cells, and ability to prevent organ damage in experimental animals. Fibronectin concentration in plasma will be assayed by an electroimmunoassay and an enzyme-linked immunoabsorbant assay, and results will be correlated with biological assays. We anticipate that our studies will allow us to develop safe, economical protocols for isolating fibronectin and administering it to patients.